Mold lock remediation

ABSTRACT

Mold lock is remediated by performing a layer-by-layer, two-dimensional analysis to identify unconstrained removal paths for any support structure or material within each two-dimensional layer, and then ensuring that aligned draw paths are present for all adjacent layers, all as more specifically described herein. Where locking conditions are identified, a sequence of modification rules are then applied, such as by breaking support structures into multiple, independently removable pieces. By addressing mold lock as a series of interrelated two-dimensional geometric problems, and reserving three-dimensional remediation strategies for more challenging, complex mold lock conditions, substantial advantages can accrue in terms of computational speed and efficiency.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/960,042 filed on Apr. 23, 2018, which claims priority to U.S. Prov.App. No. 62/580,966 filed on Nov. 2, 2017 and U.S. Prov. App. No.62/489,271 filed on Apr. 24, 2017. The entire content of each of theforegoing applications is hereby incorporated by reference.

FIELD

This disclosure relates to three-dimensional fabrication, and morespecifically to techniques for remediating mold lock in athree-dimensional fabrication process.

BACKGROUND

Mold lock occurs in three-dimensional printing when rigid supportstructures for a printed object are geometrically interlocked with theobject in a manner that provides no physical draw path for removal ofthe supports. There remains a need for techniques that automaticallyidentify and remediate mold lock conditions within three-dimensionalmodels of printed objects.

SUMMARY

Mold lock is remediated by performing a layer-by-layer, two-dimensionalanalysis to identify unconstrained removal paths for any supportstructure or material within each two-dimensional layer, and thenensuring that aligned draw paths are present for all adjacent layers,all as more specifically described herein. Where locking conditions areidentified, a sequence of modification rules are then applied, such asby breaking support structures into multiple, independently removablepieces. By addressing mold lock as a series of interrelatedtwo-dimensional geometric problems, and reserving three-dimensionalremediation strategies for more challenging, complex mold lockconditions, substantial advantages can accrue in terms of computationalspeed and efficiency.

In one aspect, a method disclosed herein may include receiving a digitalmodel including a raft, an object for fabrication on the raft, and asupport for fabrication with the object to provide physical supportaccording to one or more design rules; dividing the digital model into anumber of layers formed by planar, horizontal cross sections through thedigital model; for each layer, identifying one or more draw paths forseparating a layer of support formed by a cross section of the supportfrom a layer of the object formed by a cross section of the objectwithin the layer of the digital model; identifying one of the number oflayers as a locked layer when the layer of support has no draw path forseparating the layer of support from the layer of the object, or whenthe layer of support is vertically coupled to a second layer of thesupport having no draw path in common with the layer of support;identifying a mold locked region of the support including the lockedlayer and any vertically contiguous support layers; dividing the moldlocked region with one or more vertical planes into one or moresubregions; if the one or more subregions can be horizontally removed,processing a remaining digital model, excluding the one or moresubregions, for mold lock remediation; and if the one or more subregionscannot be horizontally removed, employing one or more three-dimensionalremediation strategies to address the mold locked region.

Dividing the mold locked region may include iteratively attempting anincreasing number of planar slices until the one or more subregions canbe horizontally removed or a threshold is reached. The one or morethree-dimensional remediation strategies may include vertically movingthe mold locked region after a second mold locked region is removed froma vertically adjacent volume. The one or more three-dimensionalremediation strategies may include subdividing the mold locked regioninto a number of volumetric subregions and searching forthree-dimensional draw paths for removing the volumetric subregions fromthe object. The volumetric subregions may be sized for removal throughan opening in the object. The method may further include, if the one ormore three-dimensional remediation strategies fail to remediate the moldlock, providing a notification to a user of an unremediated mold lockcondition. The draw path may include a range of angles over which afirst rigid shape of the cross section of the support can be separatedin a straight line from a second rigid shape of the object. Identifyingone or more draw paths may include testing for linear separation in astraight line at a number of discrete angles over a predetermined rangeof angles. The method may further include performing an initial check todetermine whether the object can be separated from the support along avertical axis. The method may further include separating regions of thesupport touching the raft from regions of the support not touching theraft along a vertical axis and performing a check to determine whetherthe object can be separated from the support along the vertical axis.The method may further include fabricating the object and the supportbased on the digital model. Fabricating the object and the support mayinclude fabricating an interface layer between the one or moresubregions of the mold locked region. Fabricating the object and thesupport may include fabricating an interface layer between the supportand the object. The design rules may include fabrication design rules.The design rules may include sintering design rules. The number oflayers may correspond to material deposition layers for an additivefabrication process.

In one aspect, a computer program product disclosed herein may includecomputer executable code embodied in a non-transitory computer readablemedium that, when executing on one or more computing devices, performsthe steps of receiving a digital model including a raft, an object forfabrication on the raft, and a support for fabrication with the objectto provide physical support according to one or more design rules;dividing the digital model into a number of layers formed by planar,horizontal cross sections through the digital model; for each layer,identifying one or more draw paths for separating a layer of supportformed by a cross section of the support from a layer of the objectformed by a cross section of the object within the layer of the digitalmodel; identifying one of the number of layers as a locked layer whenthe layer of support has no draw path for separating the layer ofsupport from the layer of the object, or when the layer of support isvertically coupled to a second layer of the support having no draw pathin common with the layer of support; identifying a mold locked region ofthe support including the locked layer and any vertically contiguoussupport layers; dividing the mold locked region with one or morevertical planes into one or more subregions; if the one or moresubregions can be horizontally removed, processing a remaining digitalmodel, excluding the one or more subregions, for mold lock remediation;and if the one or more subregions cannot be horizontally removed,employing one or more three-dimensional remediation strategies toaddress the mold locked region.

The computer program product may further include code that performs thestep of performing an initial check to determine whether the object canbe separated from the support along a vertical axis. The computerprogram product may further include code that performs the step ofseparating regions of the support touching the raft from regions of thesupport not touching the raft along a vertical axis and performing acheck to determine whether the object can be separated from the supportalong the vertical axis. The computer program product may furtherinclude code that generates instructions executable by athree-dimensional printer to fabricate the object and the support,including fabricating an interface layer between the object and thesupport and a second interface layer between the one or more subregionsof the mold locked region.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the devices,systems, and methods described herein will be apparent from thefollowing description of particular embodiments thereof, as illustratedin the accompanying drawings. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of thedevices, systems, and methods described herein.

FIG. 1 shows an additive manufacturing system.

FIG. 2 shows a method for fabricating an object.

FIG. 3 shows a mold lock condition in a fabricated object.

FIG. 4 shows a flow chart of a method for remediating mold lockconditions.

FIG. 5 illustrates an object and support that have been processed toremediate mold lock.

DESCRIPTION

Embodiments will now be described with reference to the accompanyingfigures. The foregoing may, however, be embodied in many different formsand should not be construed as limited to the illustrated embodimentsset forth herein.

All documents mentioned herein are incorporated by reference in theirentirety. References to items in the singular should be understood toinclude items in the plural, and vice versa, unless explicitly statedotherwise or clear from the context. Grammatical conjunctions areintended to express any and all disjunctive and conjunctive combinationsof conjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,” or thelike, when accompanying a numerical value, are to be construed asindicating a deviation as would be appreciated by one of ordinary skillin the art to operate satisfactorily for an intended purpose. Ranges ofvalues and/or numeric values are provided herein as examples only, anddo not constitute a limitation on the scope of the describedembodiments. The use of any and all examples, or exemplary language(“e.g.,” “such as,” or the like) provided herein, is intended merely tobetter illuminate the embodiments and does not pose a limitation on thescope of the embodiments or the claims. No language in the specificationshould be construed as indicating any unclaimed element as essential tothe practice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “up,” “down,” “above,” “below” andthe like, are words of convenience and are not to be construed aslimiting terms unless specifically stated to the contrary.

FIG. 1 shows an additive manufacturing system for use with sinterablebuild materials. The system 100 may include a printer 102, a conveyor104, and a post-processing station 106.

In general, the printer 102 may be any of the printers described hereinor any other three-dimensional printer suitable for adaptation tofabrication with sinterable build materials. By way of non-limitingexample, the printer 102 may include a fused filament fabricationsystem, a binder jetting system, a stereolithography system, a selectivelaser sintering system, or any other system that can be usefully adaptedto form a net shape object under computer control using the sinterablebuild materials contemplated herein.

The output of the printer 102 may be an object 103 that is a green bodyor the like formed of a build material including any suitable powder(e.g., metal, metal alloy, ceramic, and so forth, as well ascombinations of the foregoing), along with a binder that retains thepowder in a net shape produced by the printer 102. A wide range ofcompositions may be employed as the build material contemplated herein.For example, powdered metallurgy materials or the like may be adaptedfor use as a build material in a fused filament fabrication process orthe like. Metal injection molding materials with suitablethermo-mechanical properties for extrusion in a fused filamentfabrication process are described by way of non-limiting example inHeaney, Donald F., ed. “Handbook of Metal Injection Molding” (2012), theentire contents of which are hereby incorporated by reference.

The conveyor 104 may be used to transport the object 103 from theprinter 102 to a post-processing station 106, which may include one ormore separate processing stations, where debinding and sintering can beperformed. The conveyor 104 may be any suitable mechanism or combinationof devices suitable for physically transporting the object 103. Thismay, for example, include robotics and a machine vision system or thelike on the printer side for detaching the object 103 from a buildplatform, as well as robotics and a machine vision system or the like onthe post-processing side to accurately place the object 103 within thepost-processing station 106. In another aspect, the post-processingstation 106 may serve multiple printers so that a number of objects canbe debound and sintered concurrently, and the conveyor 104 mayinterconnect the printers and post-processing station so that multipleprint jobs can be coordinated and automatically completed in parallel.In another aspect, the object 103 may be manually transported betweenthe two corresponding stations.

The post-processing station 106 may be any system or combination ofsystems useful for converting a green part formed into a desired netshape from a metal injection molding build material by the printer 102into a final object. The post-processing station 106 may, for example,include a debinding station such as a chemical debinding station fordissolving binder materials in a solvent or the like, or more generallyany debinding station configured to remove at least a portion of thebinder system from the build material of the object 103. Thepost-processing station 106 may also or instead include a thermalsintering station for applying a thermal sintering cycle at a sinteringtemperature for the build material, or the powdered material in thebuild material, such as a sintering furnace configured to sinter thepowdered material into a densified object. The components of thepost-processing station 106 may be used in sequence to produce a finalobject. As another example, some contemporary injection moldingmaterials are engineered for thermal debinding, which makes it possibleto perform a combination of debinding and sintering steps with a singleoven or similar device. In general, the thermal specifications of asintering furnace will depend upon the powdered material, the bindersystem, the volume loading of the powdered material into the bindersystem, and other aspects of the green object and the materials used tomanufacture same. Commercially available sintering furnaces forthermally debound and sintered metal injection molding (MIM) parts willtypically operate with an accuracy of +/−5 degrees Celsius or better,and at temperatures of at least 600 degrees Celsius, or from about 200degrees Celsius to about 1900 degrees Celsius for extended times. Anysuch furnace or similar heating device may be usefully employed as thepost-processing station 106 as contemplated herein. Vacuum or pressuretreatment may also or instead be used. In an aspect, after the object103 is placed in the oven, beads of an identical or similar composition,with the addition of an unsinterable exterior coating, may be packedinto the oven with the object to provide general mechanical support witha thermally matched shrinkage rate that will not form a bond to theobject during sintering.

In the context of this description, it will be appreciated thatsintering may usefully include different types of sintering. Forexample, sintering may include the application of heat to sinter anobject to full density or nearly full density. In another aspect,sintering may include partial sintering, e.g., for a sintering andinfiltration process in which pores of a partially sintered part arefilled, e.g., through contact and capillary action, with some othermaterial such as a low melting point metal to increase hardness,increase tensile strength, or otherwise alter or improve properties of afinal part. Thus, any references herein to sintering should beunderstood to contemplate sintering and infiltration unless a differentmeaning is expressly stated or otherwise clear from the context.Similarly, references to a sinterable powder or sinterable buildmaterial should be understood to contemplate any sinterable materialincluding powders that can be sintered and infiltrated to form a finalpart.

It will also be appreciated that a wide range of other debinding andsintering processes can be used. For example, the binder may be removedin a chemical debind, thermal debind, or some combination of these.Other debinding processes are also known in the art, such assupercritical debinding or catalytic debinding, any of which may also orinstead be employed by the post-processing station 106. For example, ina common process, a green part is first debound using a chemical debind,which is following by a thermal debind at a moderately high temperature(in this context, around 700-800 Celsius) to remove organic binder andcreate enough necks among a powdered material to provide sufficientstrength for handling. From this stage, the object may be moved to asintering furnace to remove any remaining components of a binder systemand densify the object into a final part. In another aspect, a purethermal debind may be used to remove the organic binder. More generally,any technique or combination of techniques may be usefully employed todebind an object as contemplated herein.

The post-processing station 106 may be optimized in a variety of waysfor use in an office environment. In one aspect, the post-processingstation 106 may include an inert gas source 108. The inert gas source108 may, for example, include argon or other inert gas (or other gasthat is inert to the sintered material), and may be housed in aremovable and replaceable cartridge that can be coupled to thepost-processing station 106 for discharge into the interior of thepost-processing station 106, and then removed and replaced when thecontents are exhausted. The post-processing station 106 may also orinstead include a filter 110 such as a charcoal filter or the like forexhausting gasses that can be outgassed into an office environment in anunfiltered form. For other gasses, an exterior exhaust, or a gascontainer or the like may be provided to permit use in unventilatedareas. For reclaimable materials, a closed system may also or instead beused, particularly where the environmental materials are expensive ordangerous.

In one aspect, the post-processing station 106 may be coupled to othersystem components. For example, the post-processing station 106 mayinclude information from the printer 102, or from a controller for theprinter, about the geometry, size, mass, and other physicalcharacteristics of the object 103 in order to generate a suitabledebinding and sintering profile. In another aspect, the profile may beindependently created by the controller or other resource andtransmitted to the post-processing station 106 when the object 103 isconveyed. In another aspect, the post-processing station 106 may monitorthe debinding and sintering process and provide feedback, e.g., to asmart phone or other remote device 112, about a status of the object103, a time to completion, and other processing metrics and information.The post-processing station 106 may include a camera 114 or othermonitoring device to provide feedback to the remote device 112, and mayprovide time lapse animation or the like to graphically show sinteringon a compressed time scale. Post-processing may also or instead includefinishing with heat, a hot knife, tools, or similar. Post-processing mayinclude applying a finish coat.

In another aspect, the post-processing station 106 may be remote fromthe printer 102, e.g., in a service bureau model or the like where theobject 103 is fabricated and then sent to a service bureau foroutsourced debinding, sintering and so forth. Thus, for any of thesupport structures, interface layers, and so forth described below, ormore generally, for any fabricated items described below, thisdisclosure expressly contemplates a corresponding method of receiving anobject or item containing any such features, e.g., any features orstructures described below, and then performing one or morepost-processing steps including but not limited to shaping, debinding,sintering, finishing, assembly, and so forth. This may, for example,include receiving a green part with a fully intact binder system, at aremote processing resource, where the part can be debound and sinteredat the remote processing resource. This may also or instead includereceiving a brown part where some or all of the binder system has beenremoved in a debinding process at another location and the part is onlysintered at the remote processing resource. In this latter case, aportion of the binder system may usefully be retained in the part,either as a backbone binder to retain a shape of the object duringsintering until a self-supporting sintering strength is achieved, or asa residual primary binder that is left in the part to improve structuralintegrity during shipping or other handling.

More generally, this disclosure contemplates any combination anddistribution of steps suitable for centralized or distributed processinginto a final part, as well as any intermediate forms of the materials,articles of manufacture, and assemblies that might be used therein.

FIG. 2 shows a method for fabricating an object. The method 200 is morespecifically a generalized method for layer-by-layer fabrication of anobject using sinterable materials.

As shown in step 202, the method 200 may begin with providing a materialfor fabrication. This may include any of a variety of materials that canbe usefully handled in a layer-based fabrication process such as fusedfilament fabrication, binder jetting, stereolithography, and so forth.For example, this may include sinterable powders of metal, which may bebound together using a binder system or the like to retain a net shapeof an object during printing and subsequent processing into a finalobject. Interface layers of unsinterable materials, or materials thatotherwise resist bonding of an object to an adjacent support material,may be used to fabricate a separation layer for easily removable supportstructures. A number of suitable materials are described, for example,in U.S. Pat. No. 9,833,839 (incorporated herein by reference), any ofwhich may be used for the fabrication of an object, supports andinterface layers as contemplated herein. More generally, any material(s)suitable for use fabricating objects, supports and interface layers in alayer-based fabrication system may be employed as the materials in thismethod 200. It will further be appreciated that other techniques thatare not layer based, including subtractive techniques such as milling orfluid jetting, may also or instead be used, and any correspondinglysuitable materials may also or instead be employed as a build materialfor fabricating an object.

Furthermore, additional materials may be employed by a fabricationsystem, such as support materials, interface layers, finishing materials(for exterior surfaces of an object) and so forth, any of which may beused as a material for fabrication in the systems and methodscontemplated herein.

As shown in step 204, the method may include fabricating a layer for anobject. This may, for example, include a layer of the object itself or alayer of a support structure. For a particular layer (e.g., at aparticular z-axis position of a fabrication system), an interface layermay also or instead be fabricated to provide a non-sinterable interfaceor similar release layer or structure between a support structure (or asubstrate such as a raft, setter, or print bed) and an object. Inanother aspect, finishing materials for exterior surfaces may be used,such as materials that impart desired aesthetic, structural, orfunctional properties to surfaces of the object.

As shown in step 210, a determination may be made whether the object(and related supports, etc.) is complete. If the object is not complete,the method 200 may return to step 204 and another layer may befabricated. If the object is complete, then the method 200 may proceedto step 212 where post-processing begins.

As shown in step 212, the method 200 may include shaping the object.Prior to debinding and sintering, an object is typically in a softer,more workable state. While this so-called green part is potentiallyfragile and subject to fracturing or the like, the more workable stateaffords a good opportunity for surface finishing, e.g., by sanding orotherwise smoothing away striations or other artifacts of thelayer-based fabrication process, as well as spurs, burrs and othersurface defects that deviate from a computerized model of an intendedshape of the object. In this context, shaping may include manualshaping, or automated shaping using, e.g., a computerized millingmachine, grinding tools, or a variety of brushes, abrasives and so forthor any other generally subtractive technique or tool(s). In one aspect,a fluid stream of a gas such as carbon dioxide may be used to carry dryice particulates to smooth or otherwise shape a surface. In this latterapproach, the abrasive (dry ice) can conveniently change phase directlyto a gas under normal conditions, thus mitigating cleanup of abrasivesafter shaping the object.

As shown in step 214, the process 200 may include debinding the printedobject. In general, debinding may remove some or all of a binder orbinder system that retains a build material containing a metal (orceramic or other) powder in a net shape that was imparted by theprinter. Numerous debinding techniques, and corresponding bindersystems, are known in the art and may be used as binders in the buildmaterials contemplated herein. By way of non-limiting examples, thedebinding techniques may include thermal debinding, chemical debinding,catalytic debinding, supercritical debinding, evaporation and so forth.In one aspect, injection molding materials may be used. For example,some injection molding materials with rheological properties suitablefor use in a fused filament fabrication process are engineered forthermal debinding, which advantageously permits debinding and sinteringto be performed in a single baking operation, or in two similar bakingoperations. In another aspect, many binder systems may be quickly andusefully removed in a debinding process by microwaving an object in amicrowave oven or otherwise applying energy that selectively removesbinder system from a green part. With a suitably adapted debindingprocess, the binder system may include a single binder, such as a binderthat is removable through a pure thermal debind.

More generally, the debinding process removes a binder or binder systemfrom a net shape green object, thus leaving a dense structure of metal(or ceramic or other) particles, generally referred to as a brown part,that can be sintered into the final form. Any materials and techniquessuitable for such a process may also or instead be employed fordebinding as contemplated herein.

As shown in step 216, the process 200 may include sintering the printedand debound object into a final form. In general, sintering may includeany process of densifying and forming a solid mass of material byheating without liquefaction. During a sintering process, necks formbetween discrete particles of a material, and atoms can diffuse acrossparticle boundaries to fuse into a solid piece. Because sintering can beperformed at temperatures below the melting temperature, thisadvantageously permits fabrication with very high melting pointmaterials such as tungsten and molybdenum.

Numerous sintering techniques are known in the art, and the selection ofa particular technique may depend upon the build material used, the sizeand composition of particles in a material and the desired structural,functional or aesthetic result for the fabricated object. For example,in solid-state (non-activated) sintering, metal powder particles areheated to form connections (or “necks”) where they are in contact. Overa thermal sintering cycle, these necks can thicken and create a densepart, leaving small, interstitial voids that can be closed, e.g., by hotisostatic pressing (HIP) or similar processes. Other techniques may alsoor instead be employed. For example, solid state activated sinteringuses a film between powder particles to improve mobility of atomsbetween particles and accelerate the formation and thickening of necks.As another example, liquid phase sintering may be used, in which aliquid forms around metal particles. This can improve diffusion andjoining between particles, but also may leave lower-melting phase withinthe sintered object that impairs structural integrity.

It will be understood that debinding and sintering result in materialloss and compaction, and the resulting object may be significantlysmaller than the printed object. However, these effects are generallylinear in the aggregate, and net shape objects can be usefully scaled upwhen printing to create a shape with predictable dimensions afterdebinding and sintering. Additionally, as noted above, it should beappreciated that the method 200 may include sending a fabricated objectto a processing facility such as a service bureau or other remote oroutsourced facility, and the method 200 may also or instead includereceiving the fabricated object at the processing facility andperforming any one or more of the post-fabrication steps described abovesuch as the shaping of step 212, the debinding of step 214, or thesintering of step 216.

FIG. 3 shows a mold lock condition. In general, an object 300 may bethree-dimensionally printed using any of a variety of fabricationtechniques such as any of the techniques described herein. Wherenecessary or helpful for fabrication, a support 302 may be fabricatedadjacent to the object 300 to provide support for the object 300 duringfabrication and/or subsequent handling. An interface layer 304 may befabricated between the object 300 and the support 302 in order toprevent undesired bonding of the object 300 to the support 302, howeverfor certain geometries the support 302 may enclose the object 300 in amanner that does not provide any path for removal of the object 300 fromthe support 302.

In a typical fabrication process, a raft 306 may also be fabricated as asubstrate to receive the object 300 and support 302 during printing, andfabrication may be performed vertically along a vertical axis 308, oftenreferred to as the z-axis, in a layer-by-layer fashion to render aphysical realization of the object 300 above the raft 306. Some surfaces310 of the support 302 may touch the raft 306, i.e., vertically projectdownward into contact with the raft 306, and other regions 312 of thesupport 302 may not touch the raft 306, i.e., vertically projectdownward into contact with the object 300 rather than the raft 306. Asdiscussed below, an automated mold lock remediation process may addressthese regions differently.

Where the object 300 and support 302 are, e.g., sintered or otherwisethermally processed into substantially solid metal pieces or the like,removal of the support 302 can impose substantial post-fabricationprocessing in order to liberate the object 300 from the support 302,particularly where the geometry of the support 302 has no linear drawpath for separation from the object 300, a condition referred togenerally herein as mold lock. While the three-dimensional model for thesupport 302 may be modified prior to fabrication, e.g., in a computeraided design environment or the like, in order to break the support 302into a number of sub-components that can be disassembled from around theobject 300 after solidification, this is typically a labor-intensiveprocess that is often performed manually. As described below, thesechallenges may be mitigated by providing automated remediation of moldlock conditions.

FIG. 4 shows a flow chart of a method for remediating mold lockconditions. In general, when supports are generated for a part, they mayundergo a number of preliminary checks and simple modifications,followed by a systematic, two-dimensional strategy for detection andremediation of mold lock conditions. If these efforts fail, then anumber of three-dimensional remediation strategies may be employed,followed by a notification to a user if mold lock conditions defyautomated resolution. In addition to providing a number of simplifiedtwo-dimensional computational strategies for mold lock remediation, themethod 400 described below may advantageously stage remediationstrategies so that more computationally complex, three-dimensionalremediation strategies are deferred until other strategies have provenunsuccessful.

As shown in step 402, the method 400 may include receiving a digitalmodel of an object and a support structure. Receiving the model mayinclude receiving the model within a computer aided design environmentwith a user interface for user interaction, or receiving the model by atool or other program or environment configured to automate mold lockremediation as contemplated herein. In general, the model may include amodel of any object suitable for fabrication along with supportstructures to physically support the object during fabrication. Ingeneral, support structures may be automatically positioned according todesign rules for a particular fabrication process. The design rules mayinclude fabrication design rules that implicitly or explicitly specifywhere support is needed, e.g., to support bridges or overhangs in anobject during printing. The design rules may also or instead includesintering design rules that similarly specify where support is needed toprevent deformation or breakage of an object during sintering.

As noted above, during fabrication, an interface layer may be appliedbetween surfaces of the model and the support in order to preventcoupling of the two surfaces during fabrication. As more generallydescribed above, the digital model may include a raft, an object forfabrication on the raft, and a support for fabrication with the objectto provide physical support according to one or more design rules, aswell as an interface layer between any of the foregoing.

As shown in step 404, the method 400 may include performing a number ofinitial checks on the model to determine whether mold lock remediationis required. In one aspect, this may include performing an initial checkto determine whether the object can be separated from the support alonga vertical axis. While the current techniques favor two-dimensionalprocessing for purposes of computational speed and simplicity, apreliminary check may be performed on the aggregate, three-dimensionalstructure of the object and support to determine whether the object canbe simply removed, e.g., through a straight vertical motion, from thesupport, thus obviating further mold lock mitigation.

In another aspect, this may include a number of simple geometricattempts to address mold lock. For example, this may include separatingregions of the support touching the raft (and a volume vertically aboveand contiguous with such regions) from regions of the support nottouching the raft along a vertical axis and performing a check todetermine whether the object can be separated from the modifiedstructures of the support along the vertical axis. In general, thisseeks to determine whether mold lock is being created by horizontalshelves that can be addressed by simply decoupling regions below theshelf from other regions of the support structure.

Once preliminary checks based on, e.g., vertical three-dimensional drawpaths, are complete, the method 400 may proceed to other mold lockremediation steps as necessary.

As shown in step 406, the method 400 may include dividing the model intoa number of layers for processing. This may, for example, include layersformed by planar, horizontal cross sections through the digital model.In one aspect, the number of layers may correspond to materialdeposition layers for an additive fabrication process. Using thephysical deposition layers may significantly simplify processing where acurrent, fabrication-ready model or the like is already realized in anumber of layers such as layers corresponding to stereolithography crosssections or fused filament fabrication tool paths.

As shown in step 408, the method 400 may include identifying draw pathsfor removing support from the object on a layer by layer basis withinthe layers of the digital model. This may include, for each layer of thedigital model created above, identifying one or more draw paths forseparating a layer of support formed by a cross section of the supportfrom a layer of the object formed by a cross section of the objectwithin the layer of the digital model. The draw path, may for example,include a range of angles over which a first rigid shape of the crosssection of the support can be separated in a straight line from a secondrigid shape of the object, or any other single linear path or range ofcompound paths suitable for uncoupling rigid two-dimensional shapeswithin a plane. Identifying the one or more draw paths may also orinstead include testing for linear separation in a straight line at anumber of discrete angles over a predetermined range of angles, or overa continuous range of angles, or any other similar strategy forsystematically testing linear draw paths.

As shown in step 410, the method 400 may include identifying lockedlayers, e.g., layers of support with geometric features that preventdecoupling from layers of the object within the plane. In one aspect,this may include identifying one of the number of layers as a lockedlayer when the layer of support has no draw path for separating thelayer of support from the layer of the object. This may also or insteadinclude identifying one of the number of layers as a locked layer whenthe layer of support is vertically coupled to a second layer of thesupport having no draw path in common with the layer of support.

In one aspect, this may include a progressive search strategy foravailable draw paths. For example, a layer of support, or morespecifically, the two-dimensional shape of the layer in a plane, may bechecked in eight directions (e.g., two directions along four axes) forpossible movement relative to the two-dimensional shape of the object inthat plane. If a draw path is identified, other interstitial directionsmay also be checked, e.g., at half intervals to the originally checkeddirections. So, for example, where four axes are initially checked and adraw path is identified for one of the axes, the method 400 may includechecking at 22.50-degree angles about the axis of the identified drawpath.

As shown in step 412, the method 400 may include identifying lockedvolumes based on the locked layers. In general, this may includevertically traversing the layers of object and support to identifycontiguous layers of support that cannot, as a group vertically separatefrom the object. In one aspect, this includes identifying a mold lockedregion of the support including one of the locked layers of supportidentified in step 410, along with any vertically contiguous supportlayers that collectively form a locked volume.

This may also include traversing upward and/or downward from a lockedlayer until a movable layer is identified. The intervening collection oflayers, all of which are collectively locked, may then be slicedhorizontally to separate them from other groups of layers, and thesehorizontal slices may, for example, be flagged for otherthree-dimensional strategies as discussed herein. In one aspect,additional steps may be taken to prevent piecemeal, layerwiseprocessing. For example, where a single layer (or small number ofadjacent layers) is removable, but positioned immediately adjacent totwo locked layers, the removable layer may be associated with one orboth of the locked layers in order to avoid separately fabricating asingle, removable support layer. In this process, groups of movablelayers may also be formed, e.g., so that a group of adjacent layersshare at least one common draw path for horizontal removal. These groupsmay be horizontally separated from one another for independent,horizontal removal.

As shown in step 413, the method 400 may include dividing the lockedvolume of the mold locked region to attempt removal as smaller, separatepieces. This may, for example, include dividing the locked volume intoone or more subregions with one or more vertical planes through thelocked volume. This may also or instead include iteratively attemptingan increasing number of planar slices until the one or more subregionscan be horizontally removed or a threshold is reached. While this planarslicing strategy may be deployed in a deterministic manner (e.g.,bisect, and then bisect again), other strategies may also or instead beemployed. For example, planar slices may be positioned based oninformation about the aggregated draw paths for individual layers of thelocked volume. In another aspect, the planar slices may be selected andarranged to address regularly occurring use cases. For example, twoplanes intersecting at or near a centroid of the locked volume willprovide removable support structures for annular or toroidal shapes, andrelieve a number of other polygonal, two-dimensional locking conditions.

As shown in step 414, the method 400 may include evaluating theresulting structure including the subregions of support structure todetermine whether the mold lock condition has been remediated. This may,for example, include attempting horizontal removal of the subregions ofthe support from the object. If the one or more subregions can beremoved (e.g., horizontally removed), then the method 400 may proceed tostep 418 for processing of the remaining digital model. If the one ormore subregions cannot be removed, then the method 400 may proceed tostep 416 for further processing of the locked volume.

As shown in step 416, if the one or more subregions cannot behorizontally removed, the method 400 may include employing one or morethree-dimensional remediation strategies to address the mold lockedregion. In one aspect, the three-dimensional remediation strategies mayinclude vertically moving the mold locked region after a second moldlocked region is removed from a vertically adjacent volume. That is,when a portion of substrate such as a raft, or any other volume ofsupport material within the digital model, is vertically removed, thismay expose regions of support that were previously horizontallyenclosed, but can be removed vertically, such as supports within thecenter of a cylinder. In this case, it may be useful to check whetherthe separation of a region of support (e.g., using an interface layerthat permits the region to be removed after fabrication) exposes suchsupport structures for non-vertical movement. Where some vertical motionis possible but the mold locked region still cannot be extricated froman object after vertical travel, one or more horizontal slices throughthe mold locked region may usefully be employed to permit the moldlocked region to be removed in a series of horizontal segments thatindividually travel vertically and then horizontally out of engagementwith the object.

In another aspect, the three-dimensional remediation strategies mayinclude subdividing the mold locked region into a number of volumetricsubregions and searching for three-dimensional draw paths for removingthe volumetric subregions from the object. In this approach, a moldlocked region is simply subdivided into smaller volume pieces in orderto attempt removal. The volumetric subregions may, for example, be sizedfor removal through an opening in the object. More generally, anyregular or irregular pattern, such as a vertical and/or a horizontalgrid pattern, may be applied to the mold locked region of supportmaterial to attempt extraction of individual volumetric subregions.

Other strategies may also or instead be employed. For example, forinternal support structures traversing diagonally upward through anobject, it may be necessary to identify layer-to-layer overlaps so thatsufficient clearance can be added to the interface layer for travel ofthe entire support at an off-vertical angle during removal. In anotheraspect, features such as holes or openings to interior spaces may beusefully located and characterized using a number of three-dimensionalprocessing techniques, and enclosed support may be subdivided intoshapes that can be removed through such openings. These and othertechniques may be used in any of a variety of combinations to identifyand facilitate removal of support structures within a three-dimensionalobject. While some such techniques are known in the art, the method 400described herein advantageously defers many of these morecomputationally complex processing challenges, known or otherwise, untilvarious two-dimensional techniques have been applied to existingsupports.

In the event that these and other three-dimensional remediationstrategies fail to achieve a remediation of a mold lock condition, themethod 400 may include providing a notification to a user of theunremediated mold lock condition. This may include a notification withina computer aided design application, an electronic communication sentthrough other media, or some combination of these or the like. Regionsof unremediated mold lock may usefully be flagged or visuallyhighlighted within a user interface to facilitate manual inspection andremediation as appropriate. After completion of three-dimensionalremediation strategies and any other related processing steps, themethod 400 may proceed to step 418 where additional volumes may beprocessed.

As shown in step 418, the method 400 may include processing a remainingdigital model, e.g., a digital model excluding the one or moresubregions of the support that have been unlocked from the object asdescribed above, for mold lock remediation. Thus, the remediation stepsmay be repeated as needed to ensure that all of the potentially moldlocked support structures are addressed prior to fabrication.

As shown in step 420, the method 400 may include fabricating the objectand the support from the digital model, as well as the interface layerspositioned between the object and support for disassembly and removal ofthe support structure from the object after fabrication. For volumes ofsupport that have been subdivided as generally described herein,fabricating may similarly include fabricating an interface layer betweenthe one or more subregions of a mold locked region so that thesubregions can be disassembled after fabrication. In another aspect,fabricating the object (and support) may include generating instructionsexecutable by a three-dimensional printer to fabricate the object andthe support, including fabricating an interface layer between the objectand the support. This may also or instead include generatinginstructions to fabricate a second interface layer between one or moresubregions of a mold locked region, such as any of the subregionsdescribed above. Suitable instructions may be created, e.g., for any ofa number of types of printers including fused filament fabricationprinters, stereolithography printers, binder jet printers, and so forth.

FIG. 5 illustrates an object and support that have been processed toremediate mold lock. In general, an object 502 such as a ring may befabricated from a build material. Supports 504, 506, e.g., for a roof(not shown) to the object 502, may be fabricated adjacent to the object502, and separated by an interface layer 508 to prevent bonding betweenthe supports 504, 506 and the object 502 during sintering or otherpost-processing. By processing on a layer by layer basis along avertical axis 510 as described herein, the outer support 504 may beseparated in a number of locations by additional interface layers 512 tofacilitate disassembly and horizontal removal of the outer support 504after the object 502 and supports 504, 506 have been sintered into afinal part.

Additionally, after a raft (not shown) below the object 502 has beenremoved, three-dimensional strategies may be applied to recognize thatthe central support 506 can be moved vertically (downward along thevertical axis 510) for removal from the interior of the object 502. Inthis manner, all of the surrounding supports 504, 506 for the object 502may be easily removed, e.g., by hand, after the object 502 and thesupports 504, 506 have been sintered or otherwise thermally processedinto a final part such as one or more rigid, densified metalliccomponents.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable fora particular application. The hardware may include a general-purposecomputer and/or dedicated computing device. This includes realization inone or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable devices or processing circuitry, along with internal and/orexternal memory. This may also, or instead, include one or moreapplication specific integrated circuits, programmable gate arrays,programmable array logic components, or any other device or devices thatmay be configured to process electronic signals. It will further beappreciated that a realization of the processes or devices describedabove may include computer-executable code created using a structuredprogramming language such as C, an object oriented programming languagesuch as C++, or any other high-level or low-level programming language(including assembly languages, hardware description languages, anddatabase programming languages and technologies) that may be stored,compiled or interpreted to run on one of the above devices, as well asheterogeneous combinations of processors, processor architectures, orcombinations of different hardware and software. In another aspect, themethods may be embodied in systems that perform the steps thereof, andmay be distributed across devices in a number of ways. At the same time,processing may be distributed across devices such as the various systemsdescribed above, or all of the functionality may be integrated into adedicated, standalone device or other hardware. In another aspect, meansfor performing the steps associated with the processes described abovemay include any of the hardware and/or software described above. Allsuch permutations and combinations are intended to fall within the scopeof the present disclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps thereof. The code may be stored in a non-transitory fashion ina computer memory, which may be a memory from which the program executes(such as random-access memory associated with a processor), or a storagedevice such as a disk drive, flash memory or any other optical,electromagnetic, magnetic, infrared or other device or combination ofdevices. In another aspect, any of the systems and methods describedabove may be embodied in any suitable transmission or propagation mediumcarrying computer-executable code and/or any inputs or outputs fromsame.

It will be appreciated that the devices, systems, and methods describedabove are set forth by way of example and not of limitation. Absent anexplicit indication to the contrary, the disclosed steps may bemodified, supplemented, omitted, and/or re-ordered without departingfrom the scope of this disclosure. Numerous variations, additions,omissions, and other modifications will be apparent to one of ordinaryskill in the art. In addition, the order or presentation of method stepsin the description and drawings above is not intended to require thisorder of performing the recited steps unless a particular order isexpressly required or otherwise clear from the context.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So, for example, performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus, method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It should further be appreciated that the methods above are provided byway of example. Absent an explicit indication to the contrary, thedisclosed steps may be modified, supplemented, omitted, and/orre-ordered without departing from the scope of this disclosure.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A method comprising: receiving a digital modelincluding a raft, an object for fabrication on the raft, and a supportfor fabrication with the object to provide physical support according toone or more design rules; dividing the digital model into a number oflayers formed by planar, horizontal cross sections through the digitalmodel; for each layer, identifying one or more draw paths for separatinga layer of support formed by a cross section of the support from a layerof the object formed by a cross section of the object within the layerof the digital model; identifying one of the number of layers as alocked layer when the layer of support has no draw path for separatingthe layer of support from the layer of the object, or when the layer ofsupport is vertically coupled to a second layer of the support having nodraw path in common with the layer of support; identifying a mold lockedregion of the support including the locked layer and any verticallycontiguous support layers; dividing the mold locked region with one ormore vertical planes into one or more subregions; if the one or moresubregions can be horizontally removed, processing a remaining digitalmodel, excluding the one or more subregions, for mold lock remediation;and if the one or more subregions cannot be horizontally removed,employing one or more three-dimensional remediation strategies toaddress the mold locked region.
 2. The method of claim 1 whereindividing the mold locked region includes iteratively attempting anincreasing number of planar slices until the one or more subregions canbe horizontally removed or a threshold is reached.
 3. The method ofclaim 1 wherein the one or more three-dimensional remediation strategiesincludes vertically moving the mold locked region after a second moldlocked region is removed from a vertically adjacent volume.
 4. Themethod of claim 1 wherein the one or more three-dimensional remediationstrategies includes subdividing the mold locked region into a number ofvolumetric subregions and searching for three-dimensional draw paths forremoving the volumetric subregions from the object.
 5. The method ofclaim 4 wherein the volumetric subregions are sized for removal throughan opening in the object.
 6. The method of claim 1 further comprising,if the one or more three-dimensional remediation strategies fail toremediate the mold locked region, providing a notification to a user ofan unremediated mold lock condition.
 7. The method of claim 1 whereinthe draw path includes a range of angles over which a first rigid shapeof the cross section of the support can be separated in a straight linefrom a second rigid shape of the object.
 8. The method of claim 1wherein identifying one or more draw paths includes testing for linearseparation in a straight line at a number of discrete angles over apredetermined range of angles.
 9. The method of claim 1 furthercomprising performing an initial check to determine whether the objectcan be separated from the support along a vertical axis.
 10. The methodof claim 1 further comprising separating regions of the support touchingthe raft from regions of the support not touching the raft along avertical axis and performing a check to determine whether the object canbe separated from the support along the vertical axis.
 11. The method ofclaim 1 further comprising fabricating the object and the support basedon the digital model.
 12. The method of claim 11 wherein fabricatingincludes fabricating an interface layer between the one or moresubregions of the mold locked region.
 13. The method of claim 11 whereinfabricating the object includes fabricating an interface layer betweenthe support and the object.
 14. The method of claim 1 wherein the designrules include fabrication design rules.
 15. The method of claim 1wherein the design rules include sintering design rules.
 16. The methodof claim 1 wherein the number of layers correspond to materialdeposition layers for an additive fabrication process.